Thermoelectrics is involved with thermoelectric converters, which cause the generation of electric power by the Seebeck effect and refrigeration by the Peltier effect. The performance of thermoelectric conversion materials is evaluated by ZT (the figure of merit), which is expressed by the equation ZT=σS2T/κ where σ, S, κ and T are the electrical conductivity, Seebeck coefficient, thermal conductivity and absolute temperature, respectively, of the material. Materials with a large Seebeck coefficient and high electrical conductivity, but low thermal conductivity are desired.
As of today, the thermoelectric materials most commonly in use, such as alloys of Bi2Te3, have ZT values that seldom, if ever, exceed 1. They operate with poor Carnot efficiency of about 10% when compared to compressor-based refrigerators.
Akai et al in Proceedings of the 17th International Conference on Thermoelectrics (1998, pages 105-108) characterizes indium-doped cobalt antimonide produced by a solid phase reaction followed by hot-pressing. Although these materials have been used as thermoelectric materials with some effect, a need remains for thermoelectric materials having better properties.
U.S. Pat. No. 6,369,314 discloses semiconductor materials, such as skutterudite structures, useful in fabricating thermoelectric devices that are composed in part of doped cobalt antimonide compositions.
As a result of the search for improved thermoelectric materials, a composition is proposed in this invention in which cobalt antimonide is doped with indium and a second dopant. It is found that the compositions of this invention have properties making them desirable for use as thermoelectric materials.